Analysis of the resequencing delay for M/M/m systems

  • Authors:
  • Subhash Agrawal;Ravi Ramaswamy

  • Affiliations:
  • BGS Systems Inc., 128 Technology Center, Waltham, MA;BGS Systems Inc., 128 Technology Center, Waltham, MA

  • Venue:
  • SIGMETRICS '87 Proceedings of the 1987 ACM SIGMETRICS conference on Measurement and modeling of computer systems
  • Year:
  • 1987

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Abstract

Many virtual circuit service communications networks such as SNA employ virtual circuit transmission method inside the subnet. An essential feature of such networks is that the sequence in which messages are transmitted is maintained throughout the route from source node to the destination node. When there are multiple links connecting two intermediate nodes in the route and the messages are of different lengths, then it is possible that the messages complete transmission at the next node out of sequence. These messages then have to be resquenced, i.e. put in the right order, in order to provide a virtual circuit service. The resequencing operation introduces an additional delay in transmission which may be significant. In this paper the probability distribution of the resequencing delay is obtained for the M/M/m system. Simple expressions for the mean and coefficient of variation of the resequencing delay are also provided. It is shown through a variety of numerical examples that the resequencing delay is likely to be a significant component of the overall response time. Some interesting aspects of dependence of the mean resequencing delay on system parameters are studied analytically.